FWSY levain schedule question

I am new to baking. I started with FWSY book and have enjoyed some success. My question is about the difference in levain schedule for hybrid recipes and pure levain recipes. Why do the hybrid recipes call for mixing the levain at 6-8 hours while the pure levain recipes call for mixing at 7-9 hours.  
My levain tends to peak around the 12 hour mark. Should I simply wait till then in both cases or do some recipes expect the levain to be mixed at an earlier stage?

At 6-8 hour mark my levain does not pass the float test. 

Thank you!